Solid-state imaging device and method for manufacturing the same

ABSTRACT

A transfer film, on which an adhesive is applied, is glued to plural spacers formed on a glass substrate. The glass substrate is laid on a working table, and one end of the transfer film is fixed to a winding roller. A peeling guide is set at a position over the transfer film. The winding roller is driven to wind the transfer film while the working table moves horizontally. While winding the transfer film, the angle between the glass substrate and the transfer film is kept constant. After the transfer film is peeled off, the adhesive is uniformly transferred to each of the spacers.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional of U.S. application Ser. No. 11/199,992, filed Aug.10, 2005, which is a divisional of Ser. No.10/807,348 filed Mar. 24,2004, which claims priority to Japanese Application Nos. 2003-083446 and2003-320271, filed Mar. 25, 2003, and Nov. 9, 2008, respectively. Theentire disclosures are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing asolid-state imaging device by use of wafer level chip size packagingtechnique, and a solid-state imaging device manufactured by suchmanufacturing method.

2. Description of the Related Art

Digital cameras, equipped with a solid-state imaging device and asemiconductor memory device, are widely spread among consumers. Inaddition, small electric apparatus, such as a mobile phone and apersonal digital assistance (PDA), has the solid-state imaging deviceand the memory device to enable digital photography. A conventionalsolid-state imaging device is manufactured by the following steps.First, a solid-state imaging element chip, such as a charge coupleddevice (CCD) formed on a wafer, is die-bonded on a package formed from aceramic, for instance. Then, after the terminals of the solid-stateimaging element chip and the terminals of the package are electricallyconnected by bonding wires, a glass lid formed from a transparent glassis fixed to the package to seal the solid-state imaging element chip.

Small solid-state imaging device is preferable in terms of miniaturizingthe digital camera and the small electric apparatus. As for an exampleto reduce the size of the solid-state imaging device, a wafer level chipsize packaging technique (hereinafter referred to as “wafer level CSP”)can package the solid-state imaging device without the packagingmaterial. For instance, Japan Patent Laid-Open Publication (JP-A) No.2002-231921 describes the solid-state imaging device, manufactured bythe wafer level CSP technique, in which a spacer is bonded to theperipheral area of the upper surface of the solid-state imaging elementchip. The cover glass is provided on the spacer to seal the solid-stateimaging element chip. The solid-state imaging element chip hasconnection terminals on the upper, bottom or lateral surface.

In manufacturing the solid-state imaging device by the wafer level CSPtechnique, plural spacers are formed on the glass substrate as the coverglass. Then, after adhesives are applied to the edge surface of thespacers, the glass substrate is adhered to a wafer on which pluralsolid-state imaging element chips are formed. The wafer with the glasssubstrate is subject to dicing process to manufacture the solid-stateimaging device.

It is necessary to provide a space between the solid-state imagingelement and the spacer for the purpose of preventing flare that iscaused by entering incident light, reflected on the inner surface of thespacer, into the solid-state imaging element. Moreover, since the spaceris pressed onto the solid-state imaging device to generate a stressduring the bonding process, the spacer and the solid-state imagingdevice are distorted. Thus, the space between the solid-state imagingelement and the spacer is necessary for preventing such distortion tothe solid-state imaging device. Furthermore, because the solid-stateimaging element generates much heat when the solid-state imaging deviceis operated at a high clock rate or takes an image for a long exposuretime, the difference in thermal expansion rate between the solid-stateimaging element chip and the spacer causes stress. The space between thesolid-state imaging element and the spacer is necessary to prevent suchstress from affecting the solid-state imaging element.

In bonding the spacer to the wafer, if the adhesives are flowed on thesolid-state imaging element chip, the solid-state imaging device doesnot work properly because of noise interference caused by the flowedadhesive. Moreover, if the gap between the spacer and the wafer is nottightly sealed, the solid-state imaging device is damaged by coolingwater during the dicing process. Thus, in order to increaseproductivity, the spacer must be tightly bonded to the wafer.

For the purpose of proper bonding, the adhesives applied on the spacermust be thin and uniform in thickness over the applied area. Although asmall amount of adhesive with high viscosity is dropped on the spacer bypotting method according to the above publication, putting the adhesiveson the spacer having the width less than 200 μm is technicallydifficult. Even if the spacer has the width more than 200 μm, droppingthe adhesives on all bonded surfaces of the plural spacers takes toomuch time for the adhering process.

In addition the above publication describes a method to apply theadhesive to the spacer by printing, but printing the adhesive is hardlyrealized because it is difficult to control the thickness and theposition of the adhesive to be printed on the spacer. Moreover, siliconspacer tends to repel the adhesive, so it is also difficult to controlthe thickness and flatness of the adhesives to be put on the spacer.

In order to bond the spacer properly to the wafer, the width of theframe-shaped spacer is necessary to be considered. If the width of thespacer is too large, an improper bonding will happen because of airremaining inside the adhesive. Moreover, large width spacer will make itdifficult to decrease the size of the solid-state imaging device. Thus,the manufacture cost will increase because of the small number ofsolid-state imaging devices per wafer. On the other hand, if the widthof the spacer is too narrow, the solid-state imaging device will bephysically weak.

For the purpose of preventing the adhesive from flowing into thesolid-state imaging element, it is effective to lengthen the distancebetween the solid-state imaging element and the spacer. Making thedistance longer, however, will increase the manufacture cost because ofdifficulty in miniaturizing the solid-state imaging device.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method formanufacturing a solid-state imaging device that is capable of bondingthe spacers properly to the solid-state imaging elements on the wafer.

Another object of the present invention is to provide a solid-stateimaging device that is manufactured by such manufacturing method.

To achieve the above object, the solid-state imaging device ismanufactured by use of a transfer member to transfer an adhesive to aframe-shaped spacer to be bonded to a wafer on which plural solid-stateimaging elements area formed. The spacers are formed in a transparentsubstrate, and each of the spacers surrounds the solid-state imagingelement. The transfer member, which the adhesive is applied to, is stuckto the spacers. After applying the pressure to the transparent substrateand the transfer member, the transfer member is released from thetransparent substrate to transfer the adhesive layer on the spacer.

The transfer member may be a rigid body such as a glass plate. It isalso possible to form the transfer member from an elastic body, such asa flexible plastic film. The flexible film as the transfer member ispreferably peeled off in such a manner that the angle between thetransfer member and the transparent substrate is kept constant. Thetransfer member may have a ridge pattern or a recess pattern that is thesame pattern as the spacers in the transparent substrate. It is alsopossible to apply a release agent, such as silicon, on the surface ofthe transfer member.

It is possible to carry out surface modification to the surface of thespacer to which the adhesive of the transfer member is to be contacted.The viscosity of the adhesive is preferably 0.1 Pa·s or more. Theadhesive is applied to the transfer member by bar coating, blade coatingor spin coating. In addition, it is preferable to apply air pressure orroller pressure to the transfer member and the transparent substrate.

The viscosity of the adhesive at the time of transferring to the spaceris preferably 100 Pa·s to 10000 Pa·s. The thickness of the adhesive is0.5 μm to 5 μm when the adhesive is activated. The spacer may be bondedto the wafer over the surface to which the adhesive is applied.

The solid-state imaging device, manufactured by the above methods, mayhave the following features. The solid-state imaging element and theinner surface of the spacer are separated by 50 μm to 100 μm over thewhole edge of the solid-state imaging element. The width of the spaceris 100 μm to 500 μm. It is possible to form chamfer edges in the surfaceof the spacer to which the adhesive is applied. The surplus of theadhesive is contained in the space between the wafer and the chamferedges.

According to the present invention, since the adhesive is applied to thespacer by use of the transfer member with the adhesive, it is possibleto apply thin adhesive on spacers evenly at a desired thickness.Thereby, the spacers are bonded properly to the wafer without forming agap therebetween. It is also possible to prevent the adhesive from beingflowed to the solid-state imaging element.

A rigid body having high flatness as the transfer member makes itpossible to control the thickness of the adhesive. By using an elasticbody as the transfer member, the transfer member is deformed to fit thesurface of the spacers. Thus, it is possible to facilitate precisecontrol of the thickness of adhesive, without ay effect by thedifference in height of the spacers and the transparent substrate.Moreover, since the angle between the transfer member and thetransparent substrate is kept constant while the transfer member ispeeled off, it is possible to increase the uniformity of the adhesive onthe spacers.

By forming a ridge pattern that is the same as the pattern of thespacers on the transfer member, it is possible to ensure to contact ofthe transfer member to the spacers. On the other hand, a recess pattern,which is the same as the pattern of the spacers, makes it possible tocontrol the thickness of the adhesive by adjusting the depth of therecess.

A release agent on the surface of the transfer member increases thepeelability of the adhesive, so the thickness of the adhesive on thespacer may be the same as the thickness of the adhesive on the transfermember. Moreover, since surface modification to the spacer increases thewettability to the adhesive, it is possible to apply the adhesiveuniformly.

When the adhesive is applied to the transfer member, the viscosity ofthe adhesive is low (0.1 Pa·s or more). Thus, it is possible to controlthe thickness of the adhesive easily. Since the adhesive is applied tothe transfer member by bar coating, blade coating or spin coating, it ispossible to apply the adhesive evenly with high precision at a low cost.Moreover, the transfer member and the transparent substrate areuniformly pressed to each other over the whole bonded surfaces by airpressure or roller pressure.

By increasing the viscosity of the adhesive into 100 Pa·s to 10000 Pa·sat the time to transfer the adhesive to the spacer, it is possible toprevent the adhesive from being flowed out, and thus to handle thetransfer member and the transparent substrate easily at the time ofbonding. Since the thickness of the adhesive is 0.5 μm to 5 μm when theadhesive is activated, it is possible to reduce the amount of theadhesive to be flowed out of the spacer after bonding to the wafer. Suchthickness of the adhesive does not generate a gap between the spacer andthe wafer. Moreover, since the spacer is bonded to the wafer over thesurface to which the adhesive is applied, it is possible to control thebonding strength by choosing the thickness of the spacer.

The solid-state imaging element and the inner surface of the spacer areseparated by 50 μm to 100 μm over the whole edge of the solid-stateimaging element, so the flowed adhesive does not reach the solid-stateimaging element. In addition, incident light reflected on the innersurface of the spacer does not reach the solid-state imaging element.Moreover, it is possible to reduce the influence of the stress in thebonded interface between the wafer and the spacer and the thermal stresscaused by solid-state imaging element.

Since the width of the spacer is 100 μm to 500 μm, it is possible toensure even application of the adhesive. Moreover, it is possible toincrease the strength of the spacer while preventing the increase inmanufacture cost.

The surplus adhesive is contained in the space between the wafer and thechamfer edges formed in the surface of the spacer to which the adhesiveis applied, so the flowed adhesive does not reach the solid-stateimaging element.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomeeasily understood by one of ordinary skill in the art when the followingdetailed description would be read in connection with the accompanyingdrawings, in which:

FIG. 1 is a perspective view of a solid-state imaging devicemanufactured by the method according to the present invention;

FIG. 2 is a partial cross section of the solid-state imaging device;

FIG. 3 is a flow chart showing the steps to manufacture the solid-stateimaging device;

FIG. 4 is a partial cross section of a glass substrate according to themanufacture step S1, in which plural spacers are formed in the glasssubstrate;

FIG. 5 is a partial cross section of the glass substrate according tothe manufacture step S2, in which adhesive is applied to the spacers;

FIG. 6 is a flow chart showing the sequence of the manufacture step S2;

FIGS. 7A and 7B are explanatory views to illustrate the step S2-3 tostick a transfer film with adhesives to the spacer;

FIG. 8 is an explanatory view to illustrate the step S2-4 to peel thetransfer film from the spacer;

FIGS. 9A and 9B are partial cross sections to illustrate the step S3 tobond the glass substrate to the wafer;

FIG. 10 is a perspective view of the glass substrate and the wafer;

FIG. 11 is a partial cross section according to a glass substrate dicingstep S4;

FIG. 12 is a partial cross section according to a wafer dicing step S5;

FIGS. 13A and 13B are explanatory views to show the transfer film to bepeeled, according to the second embodiment;

FIG. 14 is a partial cross section of the solid-state imaging device inwhich the spacer has chamfer edges;

FIG. 15 is a flow chart showing the sequence of forming the chamferedges in the spacer;

FIGS. 16A to 16E are partial cross sections, with enlarged views, toillustrate the process to form the chamfer edges;

FIGS. 17A to 17F are explanatory views of the chamfer edges of thespacer;

FIG. 18A is an explanatory views of the transfer film and the spacer, inwhich a recess pattern to fit the spacers is formed in the transferfilm; and

FIG. 18B is an explanatory views of the transfer film and the spacer, inwhich a hollow pattern to fit the spacers is formed in the transferfilm.

PREFERRED EMBODIMENTS OF THE INVENTION

FIGS. 1 and 2 respectively show the perspective and partial crosssection of a solid-state imaging device of the wafer level CPS structurethat is manufactured by the method according to the present invention.The solid-state imaging device 2 comprises a solid-state imaging element3, a rectangular-shaped solid-state imaging element chip 5, aframe-shaped spacer 6 and a cover glass 7. The solid-state imagingelement 3 is coupled to the solid-state imaging element chip 5 viaplural terminals 4 formed on the solid-state imaging element chip 5. Thespacer 6, bonded to the solid-state imaging element chip 5, surroundsthe solid-state imaging element 3. The cover glass 7 is provided on thespacer 6 to seal the solid-state imaging element 3. The cover glass 7 ismade from a transparent α-ray shielding glass for the purpose ofprotecting the photo-diodes of the CCD.

An example of the solid-state imaging element 3 is a charge coupleddevice (CCD). There are color filters and micro lenses on the CCD. Theterminals 4 are formed on the solid-state imaging element chip 5 byprinting a conductive material. Circuit patterns between the terminals 4and the solid-state imaging element 3 are also formed by printing. Afterforming the solid-state imaging element 3 and the terminals 4 on awafer, the solid-state imaging element chips 5 are separated by dicingprocess.

The spacer 6 is formed from an inorganic material such as silicon. Thewidth W of the spacer 6 is 100 μm to 500 μm, for instance. The height Hof the spacer 6 is, for instance, 10 μm to 500 μm, and preferably 80 μmto 120 μm. An adhesive 12 to bond the solid-state imaging element chip 5and the spacer has a thickness T2 of 0.5 μm to 5 μm.

A frame-shaped surrounding area C is provided between the inner surfaceof the spacer 6 and the edge of the solid-state imaging element chip 5.The surrounding area C surrounds the whole edge of the solid-stateimaging element chip 5 for the purpose of preventing incident lightreflected on the inner surface of the spacer 6 from entering thesolid-state imaging element chip 5. The surrounding area C is alsoeffective in order not to affect the stress, generated at the interfacebetween the solid-state imaging element chip 5 and the spacer 6, to thesolid-state imaging element 3. Such stress is generated when a glasssubstrate having spacers 6 is pressed to the wafer as the base materialof the solid-state imaging element chips 5 in bonding the spacer 6.Because the solid-state imaging element generates much heat when thesolid-state imaging device 3 is operated at a high clock rate or takesan image for a long exposure time, such stress is also generated becauseof the difference in thermal expansion rate of the spacer 6 and thesolid-state imaging element chip 5.

The solid-state imaging device 2 is manufactured by the steps accordingto the flow chart of FIG. 3. In the first step S1, plural spacers 6 areformed on a glass substrate 10 used as the cover glass 7, as shown inFIG. 4. The spacers 6 are formed by the following method, for example.First, an inorganic material film, composed of an inorganic materialsuch as silicon, is layered on the glass substrate 10 by applicationtechnique such as spin coating, or by chemical vapor deposition (CVD).Then, plural spacers 6 are formed from the inorganic material film byphoto lithography, development, etching and so forth. The inorganicmaterial film may be formed on the glass substrate 10 by bonding asilicon wafer to the glass substrate 10. Alternatively, an inorganicmaterial may be directly printed on the glass substrate 10 to form thespacer 6.

As shown in FIG. 5, a thin adhesive 12 is uniformly applied on edgesurfaces of the spacer 6, to be glued to the wafer, on the glasssubstrate 10. The adhesive 12 for gluing the spacer 6 to the wafer isrequired to prevent deformation upon activation, and to keep inwater-tight manner. Examples of the adhesives 12 are room-temperatureactivated adhesives of epoxy resins, silicon resins, and so forth. Forthe purpose of controlling the thickness in application, the adhesives12 preferably have viscosity V1 about 0.1 Pa·s to 10 Pa·s. Other typesof adhesives, such as UV activated adhesives, visible light activatedadhesives and heat activated adhesives, may be used as the adhesive 12,if these adhesives yield the same effect.

The adhesive 12 is applied to the spacers 6 by the steps S2-1 to S2-4,which are shown in FIGS. 6, 7A, 7B and 8. In the step S2-1, a transferfilm 16 is laid on a flat work table 15, as shown in FIG. 7A. The worktable 15 is made of glass with high flatness, for instance. The transferfilm 16, used as a transfer member, is laid on the working table 15 byair suction or electrostatic chuck, such that the transfer film 16neither have wrinkles nor shift the position on the working table 15.

The transfer film 16 is a flat and thin film that is made ofpolyethylene terephthalate (PET). The transfer film 16 has a shapelarger than the glass substrate 10. A coating bar 17 for bar coaterapplies the adhesive 12 uniformly on the transfer film 16 on the workingtable 15. The thickness T1 of the adhesive 12 on the transfer film 16 is6 μm to 10 μm, preferably 8 μm. It is possible to utilize other type ofcoater, such as a blade coater and a spin coater.

It is known that an optical room-temperature activated adhesive is notgood in wettability to an inorganic material (such as silicon) used asthe spacer 6, and that the wettability improves by increasing theviscosity. An adhesive with high viscosity, however, makes it difficultto control the thickness in application to the spacer 6. Thus, themanufacture process according to the embodiment includes a step S2-2 toleave the transfer film 16 for a predetermined time after the adhesive12 is applied, so the viscosity of the adhesive 12 increases. In thisstep S2-2, the temperature and the predetermined time are adjusted suchthat the viscosity of the adhesive 12 increases to V2, for transfer tothe spacer 6, from V1 that is the initial viscosity at the time ofapplication to the transfer film 16. The viscosity V2 is 100 Pa·s to10000 Pa·s, for instance, and preferably about 2000 Pa·s to about 3000Pa·s.

By using the adhesive 12 with low viscosity at the time of applicationto the transfer film 16, and by increasing the viscosity fortransferring the adhesive 12 to the spacer, it is possible to controlthe thickness of the adhesive 12 precisely while keeping a highwettability to the spacer 6. Since the adhesive 12 with high viscositydoes not flow easily, it is possible to handle the transfer film 16, andthe glass substrate 10 easily after transfer of the adhesive 12.Moreover, if the adhesive 12 has high viscosity, it is possible toreduce the amount of the adhesive 12 squeezed out of the spacer 6 inbonding the spacers 6 onto the wafer 26.

In the event that the adhesive 12 is hydrophilic, the spacer 6 mayimprove its wettability to the adhesive 12 by surface modification, suchas application of plasma or ultraviolet rays.

In the step S2-3, the glass substrate 10 is glued to the transfer film16 by hand or by use of an alignment equipment. An example of thealignment equipment is depicted in FIG. 7B. The alignment equipmentcomprises a glass holder table 20 and a film holder table 21. The glassholder table 20 holds the glass substrate 10 by air suction throughsuction holes 20 a. The film holder table 21 holds the transfer film 16via a sponge 21 b by air suction from suction holes 21 a. The filmholder table 21 is moveable up and down (vertical direction in thedrawing) in the same manner as a well-known Z-axis movement table.

The film holder table 21 holds the transfer film 16 on the sponge 21 bafter application of the adhesive 12, and moves upward to uniformlypress the transfer film 16 onto the spacers 6 that is formed on theglass substrate 10. The sponge 21 b needs to have enough strength topress the transfer film 16 firmly onto the spacer 6 without breaking thespacer 6. Thereby, the glass substrate 10 is glued to the transfer film16 since the film holder table 21 ensures the spacer 6 to contact to theadhesive 12 on the transfer film 16. The glass substrate 10 may be gluedto the transfer film 16 by moving a pressure roller on the glasssubstrate 10.

During the step S2-4, the transfer film 16 is peeled off, and thereby,the adhesives 12 are transferred to the spacers 6. As shown in FIG. 8, afilm peeling equipment used in this step comprises a working table 22, awinding roller 23 and a peeling guide 24. The working table 22 to holdthe glass substrate 10 by air suction, for instance, is slidablehorizontally by a table moving mechanism used for a well-known XY table.One end of the transfer film 16 is fixed to the winding roller 23. Thepeeling guide 24 comes in contact with the upper surface of the transferfilm 16, and keeps the angle θ between the transfer film 16 and theglass film 10 constant.

The film peeling equipment starts to drive the winding roller 23 to windthe transfer film 16 at the same time as sliding the working table 22 toleftward in the drawing. Thereby, the transfer film 16 is peeled offfrom one end of the glass substrate 10. Since the shape of the rearsurface of the transfer film 16 is regulated by the peeling guide, theangle θ between the transfer film 16 and the glass film 10 becomesconstant. Thus, the thickness of the transferred adhesive 12 becomesuniform. If the transfer film 16 is not large enough to engage thewinding roller 23, an extension film is attached to one end of thetransfer film 16 such that the transfer film 16 is fixed to the windingroller 23.

In the third step S3, the glass substrate 10 is bonded to the wafer 26on which plural solid-state imaging elements 3 and the connectingterminals 4 are formed, as shown in FIG. 9A. Note that the glasssubstrate 10 and the wafer 26 have the same size and shape (see FIG.10). An alignment bonding equipment, used for bonding the glasssubstrate 10 to the wafer 26, comprises a bonding table 28 andpositioning table 29. The bonding table 28 holds and positions the wafer26 by air suction through air suction holes 28 a. The positioning table29 holds the glass substrate 10 by air suction through air suction holes29 a, and adjusts the position of the glass substrate 10 in the XYdirection (horizontal direction) and the angle to fit the position andangle of the wafer 26.

The positioning table 29 adjusts the position of the glass substrate 10by use of orientation flat lines 26 a, 10 a of the wafer 26 and theglass substrate 10, and alignment marks that are properly formed in thewafer 26 and the glass substrate 10. After positioning, the positioningtable 29 moves downward to stick the glass substrate 10 on the wafer 26.Then, pressure is applied to the whole surface of the glass substrate 10at a relatively weak pressure so that the glass substrate 10 isprovisionally bonded to the wafer 26. Note that the alignment bondingequipment for provisional bonding does not have the sponge used for thealignment equipment (see FIG. 7B), because the spacer 6 needs to beprecisely positioned with respect to the solid-state imaging element 3in bonding the glass substrate 10 to the wafer 26.

After provisional bonding by use of the alignment bonding equipment, thewafer 26 with the glass substrate 10 is transferred to a pressurebonding equipment, as shown in FIG. 9B. The pressure bonding equipmentcomprises a bonding table 30 and a pressure table 33. The bonding table30 holds the wafer 26 and the glass substrate 10 at a predeterminedposition by air suction through air suction holes 30 a. The pressuretable 33, provided above the bonding table 30, presses the glasssubstrate 10 at a predetermined uniform pressure via a sponge 33 a. Inorder to ensure firm bonding, the pressure bonding equipment presses theglass substrate 10 and the wafer 26 for a predetermined time until theadhesive 12 is activated.

The width W of the framed portion of the spacer 6 affects the strengthand the condition in bonding between the spacer 6 and the wafer 26, aswell as the strength of the spacer 6 itself. If the width W of thespacer 6 is too large, an improper bonding tends to happen because ofair remaining inside the adhesive 12. Moreover, since the spacer 6becomes larger, it is difficult to decrease the size of the solid-stateimaging device 2. Thus, the manufacture cost will increase because ofthe small number of solid-state imaging devices 2 per wafer 26. On theother hand, making the width W of the spacer 6 narrow will decrease thephysical strength of the spacer 6 and the bonding strength between thespacer 6 and the wafer 26.

In this embodiment, the width W of the spacer 6 is appropriatelyselected within the range from 100 μm to 500 μm, in accordance with thesize of the solid-state imaging element 3. For instance, if thesolid-state imaging element 3 is 1/7 inch in size, the solid-stateimaging device 2 is designed such that the width W of the spacer 6 is200 μm. Thereby, it is possible to increase the strength of the spacer6, to prevent improper bonding and not to decrease the number of thespacers 6.

As shown in the enlarged portion in FIG. 2, the adhesive 12 is partiallyflowed out from the spacer 6 when the glass substrate 10 is pressed ontothe wafer 26 by use of the pressure bonding equipment. If the amount offlowed adhesive 12 is large enough to reach the solid-state imagingelement 3, such adhesive 12 will generate noise interference in theoperation of the solid-state imaging device 2. The adhesive 12 accordingto the embodiment has high viscosity in bonding, so the amount (lengthfrom the spacer 6) of the flowed adhesive 12 becomes small. Moreover,since the flowed adhesive 12 is kept to the surrounding area C betweenthe spacer 6 and the solid-state imaging element 3, it is possible toprevent the adhesive 12 from flowing into the solid-state imagingelement 3.

If the surrounding area C is too narrow, the adhesive 12 is easilyflowed into the solid-state imaging element 3. In addition, thesolid-state imaging element 3 will be affected by incident lightreflected on the inner surface of the spacer 6, and the stress at theinterface between the spacer 6 and the wafer 26. On the other hand,making the surrounding area C too wide is not preferable in terms ofproductivity and manufacture cost.

The applicant carried out an experiment to analyze the relationshipbetween the viscosity of the adhesive 12 and the amount of flowedadhesive 12. In this experiment, the length of the adhesive from theinner surface of the spacer is measured after bonding the spacer to thewafer. The viscosity of the adhesive is varied in this experiment. As aresult, it is found that the length of the flowed adhesive becomes smallas the viscosity of the adhesive increases. Especially, the length ofthe flowed adhesive 12 becomes less than 65 μm when the viscosity V2 ofthe adhesive 12 at the time of transfer is 100 Pa·s to 10000 Pa·s(preferably, about 2000 Pa·s to about 3000 Pa·s).

Accordingly, designing the width of the surrounding area C within therange from 50 μm to 100 μm, preferably from 65 μm to 80 μm, makes itpossible to prevent the adhesive 12 from flowing into the solid-stateimaging element 3 while making the solid-state imaging device as smallas possible. Moreover, designing the width of the surrounding area Cwithin the above range is effective in getting rid of the influence ofreflected incident light and the stress at the interface of the spacer6.

As shown in the enlarged view in FIG. 2, the thickness T2 of theactivated adhesive 12 becomes smaller than the thickness T1 of theadhesive 12 applied to the transfer film 16. This is because theadhesive 12 is partially remained on the transfer film 16 aftertransferring the adhesive 12 top the spacer 6, and because the adhesive12 is partially flowed out of the spacer when the spacer 6 is bonded tothe wafer 26.

An experiment carried out by the applicant shows that the spacer 6 isfirmly bonded on the solid-state imaging element chip 5 without a gaptherebetween if the thickness T2 of the activated adhesive 12 is 0.5 μmto 5 μm. Thus, the thickness T1 of the adhesive 12 in transferring tothe transfer film 16 need to be determined in consideration of theamount of remained adhesive and flowed adhesive, such that the thicknessT2 of the activated adhesive 12 is 0.5 μm to 5 μm.

In the fourth step S4, the glass substrate 10 is subject to dicingprocess by use of a diamond cutter 31 to divide the glass substrate 10into plural cover glasses 7, as shown in FIG. 11. Cooling water ispoured from the nozzles 32 in order to prevent overheating of thediamond cutter 31 and the glass substrate 10. Since the adhesive 12seals the gap between the spacer 6 and the wafer 26 in water-tightmanner, the cooling water does not flow into the spacer 6 during theglass substrate dicing step S4.

During the fifth step S5, a dicing tape 34 is glued to the bottomsurface of the wafer 26, as shown in FIG. 12. Then, a diamond cutter 35is actuated to dice the wafer 26 while pouring the cooling water fromnozzles 36, and thereby, plural solid-state imaging devices 2 aremanufactured. The adhesive 12 between the spacer 6 and the wafer 26tightly keeps the cooling water from the nozzles 36 from flowing intothe spacer 6.

Although the transfer member is a flexible plastic film in the aboveembodiment, a rigid body with high flatness may be used as a transferplate 38 for transferring the adhesive 39 to the spacer 6, as shown inFIG. 13A. The transfer plate 38 is, for instance, a glass plate. In theevent of transferring the adhesive 39 by use of the transfer plate 38,it is necessary to release the transfer plate 38 slowly from the glasssubstrate 10 for the purpose of ensuring to transfer the adhesive 39 tothe spacer 6.

As shown in FIG. 13A, a release agent 37, such as silicon, may be coatedon the surface of the transfer plate 38 for the purpose of increasingthe peelability of the adhesive 39 from the transfer plate 38. In thatcase, any type of the adhesive 39 may be used if it is possible to applythe adhesive 39 to the release agent 37, and if the wettability of theadhesive 39 to the spacer 6 is better than that to the release agent 37.

In FIG. 13A, the adhesive 39 is applied to the release agent side of thetransfer plate 39. Then, the transfer plate 38 is released from theglass substrate after sticking the transfer plate 38 to the spacer 6, asshown in FIG. 13B. The adhesive 39 on the release agent 37 is completelytransferred to the spacer 6 over the area where the adhesive 39 comes incontact with the spacer 6.

The thickness T3 of the adhesive 39 on the transfer plate 38 is the sameas the thickness T4 of the adhesive 39 transferred to the spacer 6.Accordingly, the thickness of the adhesive 39 transferred to the spacer6 is easily controlled by adjusting the thickness of the adhesive 39applied on the transfer plate 38. The adhesive 39 with high viscosity ispreferable. The release agent 37 is also applied to the transfer film 16as the transfer member. It is also possible to provide a silicon coatfilm.

As shown in FIG. 14, the solid-state imaging device 40 may have a spacer41 in which chamfer edges 43 are formed in the surface to be bonded tothe solid-state imaging element chip 42. The space between the chamferedges 43 and the solid-state imaging element chip 42 can contain thesurplus adhesive 44 to be flowed out, so it is possible to reduce theamount of the adhesive 44 to flow toward the solid-state imaging element45. Accordingly, the surrounding area C between the spacer 41 and thesolid-state imaging element 45 is reduced.

The chamfered edges 43 may be formed according to the steps S11-S15shown in FIG. 15. In the first step S11, an adhesive 51 is applied on aglass substrate 50 as the base material of the cover glass 47 (see FIG.16A). The glass substrate 50 is bonded to a spacer wafer 52 as the basematerial of the spacer 41. In the second step S12, a resist mask 53 isformed on the spacer wafer 52 (see FIG. 16B). The resist mask 53corresponds to the pattern of the spacers 41.

In the third step S13, the spacer wafer 52 is subject to isotropic dryetching to remove the spacer wafer 52 in the area that is not covered bythe resist mask 53. Thereby, the chamfer edges 43 are formed underneaththe resist mask 53, as shown in FIG. 16C. Then, in the fourth step S14,the spacer wafer 52 is subject to anisotropic dry etching to remove thespacer wafer 52 vertically, as shown in FIG. 16D. In the fifth step S15,the resist mask 53 and the adhesive 51 are removed by ashing process toform the plural spacers 41 on the glass substrate 50 (see FIG. 16D).

Besides the flat edge in FIG. 2 and the chamfer edge in FIG. 14, thespacer may have other edge shapes. Examples of the edge shapes areconvex, concave, taper, semi-circle, steps, and quarter circle, as shownin FIGS. 17A-17F. The spacers with these edge shapes can contain thesurplus of the adhesive 12, and thus reduces the amount of the adhesive12 to be flowed toward the solid-state imaging element 45.

As shown in FIG. 18A, a transfer member 60 may have a ridge pattern 60 athat fits the spacers 6 formed in the glass substrate 10. An adhesive 61is applied to the transfer member 60 with the ridge pattern 60 a. Byforming the ridge pattern 60 a, it is possible to ensure the contact ofthe transfer member 60 to the spacer 6. Alternatively, a transfer member65 may have recess pattern 65 a that first the spacers 6, as shown inFIG. 18B. An adhesive 66 is applied to the transfer member 65 with theridge pattern 65 a. It is possible to adjust the amount of the adhesive66 by controlling the depth of the recess pattern 65 a. An elastic bodylike a flexible film and a rigid body like a glass plate may be used asthe transfer member 60, 65.

The CCD type solid-state imaging device is described in the aboveembodiment, a CMOS type solid-state imaging device is applied to thepresent invention. The present invention is also applicable to bonding asubstrate to manufacture a chip with CSP structure other than thesolid-state imaging device.

Various changes and modifications are possible in the present inventionand may be understood to be within the scope of the present invention.

1. A solid-state imaging device manufactured by sticking a transparentsubstrate, in which plural frame-shaped spacers are formed, via anadhesive to a wafer on which plural solid-state imaging elements areformed, and by dividing the transparent substrate and the wafer for eachsolid-state imaging element, each of the solid-state imaging elements onthe wafer being surrounded by each of the spacers, the methodcomprising: sticking a transfer member, to which the adhesive isapplied, to the spacer; applying pressure to the transparent substrateand the transfer member; and releasing the transfer member from thetransparent substrate to transfer the adhesive on the spacer.
 2. Thesolid-state imaging device according to claim 1, wherein the solid-stateimaging element and the inner surface of the spacer are separated by 50μm to 100 μm over the whole edge of the solid-state imaging element. 3.The solid-state imaging device according to claim 1, wherein the widthof the spacer is 100 μm to 500 μm.
 4. The solid-state imaging deviceaccording to claim 1, wherein chamfer edges are formed in the surface ofthe spacer to which the adhesive is applied, the surplus adhesive iscontained in the space between the wafer and the chamfer edges.